The present invention is directed to a sole structure in a shoe, e.g., a sports shoe, the sole structure comprising an outer, wearing sole, an inner or intermediate layer for contact with a foot within the shoe, and a cushioning and supporting structure between the sole and the layer.
Running shoes, especially for marathon and other long-distance running races, have two basic requirements. The principal task of the shoe is to help the act of running, so that the runner moves forwardly as sparingly as possible. The other task of the shoe is to protect the feet for running exertion, so that conditions for the runner's optimum performance may also be preserved or maintained through the latter part of a running race. To achieve the aforementioned functions, many different shoes have been developed with resilient sole structure to reduce the exertion directed to the runner's feet.
Resilience of the sole can be obtained in many different ways. For example, an air cushion structure can be used or the sole can be constructed of several layers, one upon the other, the hardness and density of which vary to achieve progressive flexibility. However, a disadvantage in the previously-known shoes is that during the act of running, when the shoe is placed against the running ground, marked and unnecessary deformations take place in the shoe sole, so that the shoe sole returns to its original form only when the shoe is in the air. The runner wastes in this fashion a great deal of energy only for the deformation of the shoe sole.